1. Field of the Invention
The present invention relates to a method of drying a resinous composition layer using vacuum drying, a method of manufacturing color filter substrate using this drying method, and a liquid crystal display device.
2. Related Background Art
In a color filter for a liquid crystal display and for a video camera, it is now indispensable for obtaining a higher contrast and a higher resolution to form a black matrix. A method of forming the black matrix may be roughly classified into a method using a metal film of chrome etc. and a method of using a black resin.
In the case of using the metal film, a typical method is that in advance of forming pixels in respective colors such as red (R), green (G) and blue (B), a metal film of chrome etc. is provided on a transparent substrate by sputtering, and thereafter the black matrix is formed via a photolithography process and an etching process. This method, however, requires vacuum layer forming equipment and has a large number processes, which leads to a rise in manufacturing costs. Further, if eventually applied to a display device, a defect is that the screen is hard to be watched because of a reflection peculiar to the metal film.
What is most typical among the methods involving the use of the black resin, is a method of previously forming the black matrix composed of the black photosensitive resin by the photolithography, and sequentially forming the respective pixels in red, green and blue inside the black matrix by the photolithography.
Further, Japanese Patent Application Laid-Open No. 9-133807 discloses a method of forming a light-shielding layer (black matrix) extending between the red, green and blue pixels by coating, over the entire surface of a transparent substrate formed beforehand with the red, green and blue pixels, a black resist containing a cationic polymerizing compound, a black pigment, a light acid producing agent and a solvent so that all gaps between the red, green and blue pixels are filled with the black resist, then drying the coated substrate, subsequently a non-coated surface (the surface of the transparent substrate) of the substrate is exposed to beams of ultraviolet light, executing thermal hardening and development after the exposure, and thereby forming the light shielding layer (black matrix) extending between the red, green and blue pixels.
According to this method, however, after finishing the coating of the black resist, and the coated substrate is heated (pre-baked) at 50xc2x0 C. to 100xc2x0 C. for 1 min. to 10 min. by use of a hot plate and an oven, thereby removing the residual solvent and drying the substrate. Therefore, the resist starts reacting, resulting in such a problem that a developing characteristic might decline in several hours.
On the other hand, Japanese Patent Application Laid-Open No. 6-97061 discloses a method of forming an interference preventive coated film containing a water content by coating a water-soluble reflection preventive film material over a resist film formed through a coating process and a heat-drying (pre-baking) process, and forming a reflection preventive film by drying the interference preventive coated film in vacuum. According to this method, the solvent is water, and hence the drying process requires a vacuum state as high as 0.01 Torr and a processing time as long as 120 sec. under this high vacuum state. Further, a pump system becomes expensive in order to obtain the vacuum degree of 0.01 Torr.
The present inventors have examined a possibility of an application of the above-described vacuum-drying method when drying the resist, and it has proven that there arise problems peculiar to the pigment dispersed resist such as occurrences of defects in which a foreign matter exists on the surface, a pinhole is formed, and the material is coagulated in the case of drying the resist, wherein the vacuum degree is set to 1 Torr under normal operating conditions by use of a prior art vacuum drying device.
The present invention has been made to solve the above-mentioned problems, and therefore has an object to provide a resinous composition layer drying method capable of forming a resinous layer exhibiting less deterioration of a developing characteristic with an elapse of time without causing defects such as a foreign matter on the surface, a pinhole, and a coagulation of the material.
To accomplish this object, according to the present invention, there is provided a method of drying a resinous composition layer, comprising the steps of: coating a resinous composition over a substrate; and drying the resinous composition layer to be dried, characterized in that the drying method is a vacuum dry, and a drying condition in that case is such that an exhaustion is performed taking over 6 sec. till a degree of vacuum comes to 100 Torr.